170 HYPERFINE COUPLINGS IN VIVO & IN VITRO TYROSINE RADICALS

SIR提供L-[B_2H_2]色氨酸100 mg和L-[4' _17 O]Tyrosine酪氨酸自由基存在于多种酶系统中 包括核糖核苷酸、还原酶、前列腺素合酶 光系统111和半乳糖氧化酶。 自旋密度分布 可能会被环境因素改变，其中一些可能是关键的 酶结合自由基的功能。 我们参与了 通过EPR光谱表征这些自由基，以便 确定自旋密度。 最近的研究表明， 核糖核苷酸中酪氨酸中酚氧位置的r 还原酶，在光系统H，和酪氨酸的化学模型。 本研究旨在阐明特定的蛋白质-自由基相互作用 有助于酶的功能。 我们建议访问自旋 用[4 '-170]酪氨酸标记酚氧的密度。 通过 我们与布里特-玛丽·斯杰伯格教授的斯德哥尔摩小组合作， 获得了70标记酪氨酸自由基的EPR谱， 核糖核苷酸还原酶，我们寻求获得互补模型 和光系统H数据。 模型17 O-标记的酪氨酸自由基将 由我们开发的UV技术产生[巴里等人，1990 JBC 265，20139-20141）。 将掺入17个O-标记的酪氨酸 通过使用营养缺陷型 我们已经描述过的情况（巴里和巴布科克，1987年 Proc. Natl. Acad. Sci. USA，84，7099-7103）。 EPR光谱将 就像这些早期的研究一样。 细菌的活性部位 甲胺氧化酶含有一个新的氧化还原辅基 由两个色氨酸组成的色氨酸醌 redidues. p-氘代色氨酸将用于探测自旋 辅因子的丝醌式中的密度分布。

The SIR provided L-[B_2 H2]Tryptophan; 100mg and L-[4' _17 O]Tyrosine Tyrosine radicals occur in a variety of enzyme systems including ribonucleotide, reductase, prostaglandin synthase, Photosystern 111, and galactose oxidase. Spin density distributions can be altered by environment factors, some of which may be critical for the function of enzyme-bound radicals. We have been involved in characterizing these radicals by EPR spectroscopy in order to determine spin-density. Recent work suggests substantial variation in r at the phenol oxygen position in tyrosines in ribonucleotide reductase, in Photosystem H, and in a chemical model of tyrosine. This study aims at elucidating particular protein-radical interactions that contribute to enzyme function. We propose to access the spin density at the phenolic oxygen by labeling with [4'- 170]tyrosine. By collaborating with the Stockholm group of Prof Britt-Marie Sj6berg, we have obtained the EPR spectrum of the '70_ labeled tyrosine radical in ribonucleotide reductase, and we seek to obtain complementary model and Photosystem H data. Model 17 O-labeled tyrosine radicals will be generated by the UV techniques we have developed [Barry et al., 1990 JBC 265, 20139-20141). 17 O-labeled tyrosine will be incorporated into the cyanobacterium Synechocystis by using the auxotrophic condition that we have already described (Barry and Babcock, 1987 Proc. Natl. Acad. Sci. USA, 84, 7099-7103). EPR spectroscopy will be done as in these earlier studies. The active site of bacterial methylamine dehydrogenases contains a novel redox prosthetic group tryptophan tryptophanyl quinone that is made up of two tryptophan redidues. P-Deuterated tryptophan will be used to probe the spin density distribution in the serniquinone fon-n of the cofactor.